Endometrial ablation (i.e., the removal or destruction of the endometrial lining of the uterus) is used as an alternative to hysterectomy for treating abnormal uterine bleeding due to benign disease. The standard techniques for performing endometrial ablation employ a resectoscope (i.e., a hysteroscope with a built-in wire loop or other shaped device) that is inserted transcervically into the uterus, and uses radio-frequency electrical current (RF current) to remove or coagulate the endometrial tissue. These standard techniques typically are performed in a hospital setting.
During recent years, the medical industry has been developing simpler procedures, some of which are targeted for use in performing endometrial ablation in an office setting. Cryogenic ablation, or “cryoablation”, is one such procedure. Cryoablation typically is performed using a straight, small-diameter probe, about 5 to 10 mm in diameter, that is inserted transcervically into the uterus. One such probe is described in U.S. Pat. No. 6,306,129. The probe is cooled to cryogenic temperatures, e.g., by circulation of a cryogenic fluid inside the probe. At a temperature of −90° C. or below, ice forms around the probe, freezing tissue in the endometrium (i.e., the lining) and myometrium (i.e., the muscle layer below the lining) of the uterus. The edge of the ice formation has a temperature of about 2° C., which is non-destructive of tissue. At a distance of about 4 mm within the ice ball, the temperature is about −20° C., which is sufficiently cold to destroy the endometrial tissue. A number of placements of the probe may be needed to destroy the lining of the entire cavity, but, typically, 2 to 3 ice balls are sufficient. Placement of the probe and formation of the ice ball can be visualized by abdominal ultrasound or other non-invasive imaging techniques. Such visualization facilitates complete ablation of the entire cavity and allows the doctor to control the formation of the ice ball to prevent unwanted tissue damage, e.g., freezing of the uterine serosa or other tissues surrounding the uterus.
A disadvantage of the cryoablation techniques known to the art arises from the need to create multiple ice formations to ablate the entire lining of the uterus. This need arises primarily because of the approximately triangular shape of the uterus and the volume of the uterus, which is too large to treat with a single ice ball. While it is usually practical to withdraw the probe from the surrounding ice ball, the presence of the ice formation within the uterus can make it difficult, if not impossible, to correctly position the probe for formation of the second or third ice formation. The withdrawal and repositioning of the probe also requires a significant amount of time.
There remains a need for a cryoablation tool that can be used to treat the entire intrauterine surface in a single freezing step. Moreover, the tool, as well as the procedures in which it is employed, should be suitable for use in a doctor's office.